[PATCH v2] Add call to non-crashing cores through IPI

[Per Fransson]

v2 changes:
* the interrupts of the calling core are no longer disabled
  before performing the IPI
---

When kexec is used to start a crash kernel the other cores
are notified. These non-crashing cores will save their state
in the crash notes and then do nothing.

Signed-off-by: Per Fransson <per.xx.fransson at stericsson.com>
---
 arch/arm/kernel/machine_kexec.c |   27 +++++++++++++++++++++++++++
 1 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index 3a8fd51..57a7f2f 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -23,6 +23,8 @@ extern unsigned long kexec_indirection_page;
 extern unsigned long kexec_mach_type;
 extern unsigned long kexec_boot_atags;
 
+static atomic_t waiting_for_crash_ipi;
+
 /*
  * Provide a dummy crash_notes definition while crash dump arrives to arm.
  * This prevents breakage of crash_notes attribute in kernel/ksysfs.c.
@@ -37,9 +39,34 @@ void machine_kexec_cleanup(struct kimage *image)
 {
 }
 
+void machine_crash_nonpanic_core(void *unused)
+{
+	struct pt_regs regs;
+
+	crash_setup_regs(&regs, NULL);
+	printk(KERN_EMERG "CPU %u will stop doing anything useful since another CPU has crashed\n",
+	       smp_processor_id());
+	crash_save_cpu(&regs, smp_processor_id());
+	flush_cache_all();
+
+	atomic_dec(&waiting_for_crash_ipi);
+	while (1)
+		cpu_relax();
+}
+
 void machine_crash_shutdown(struct pt_regs *regs)
 {
+	unsigned long msecs;
+
 	local_irq_disable();
+
+	atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
+	smp_call_function(machine_crash_nonpanic_core, NULL, false);
+	msecs = 1000; /* Wait at most a second for the other cpus to stop */
+	while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
+		mdelay(1);
+		msecs--;
+	}
 	crash_save_cpu(regs, smp_processor_id());
 
 	printk(KERN_INFO "Loading crashdump kernel...\n");
-- 
1.7.2.2